Well, this article from Lifehacker has one of Jerry Seinfeld’s secrets. And I quote…

He (Seinfeld) told me to get a big wall calendar that has a whole year on one page and hang it on a prominent wall. The next step was to get a big red magic marker.

He said for each day that I do my task of writing, I get to put a big red X over that day. "After a few days you’ll have a chain. Just keep at it and the chain will grow longer every day. You’ll like seeing that chain, especially when you get a few weeks under your belt. Your only job next is to not break the chain."

"Don’t break the chain." He said again for emphasis.

Of course, the other secret of his success was to stick to his vision. He has a clear "no hugging, no learning" rule for his sitcom. Part of the reason that Seinfeld is such a great series is that the characters don’t grow or learn. They just are what they are. Such clear statements of purpose.

Don’t break the chain!